Apparatus for charging a liquid with gas

ABSTRACT

In producing carbonated water, CO2 gas from a storage tank is introduced into a charging chamber together with a water spray delivered by a double-acting pump. The charged water is collected in a reservoir from which a portion of the evolving gas is directed to the pump for reciprocating same; on its way to the pump, this gas flow passes through a pair of control valves held open by gas pressure from another reservoir outlet as long as the liquid in that reservoir remains below a predetermined level. When this level is reached, a float cuts off the gas pressure so that the control valves close to arrest the pump. Reciprocation of the pump piston is controlled by a switching valve which is temporarily locked in a terminal phase of each piston stroke to stress a spring in a lost-motion coupling between the piston and the valve body, the subsequent release of the locking detent enabling the instant reversal of the switching valve by snap action.

United States Patent 1 Tremolada 1 Sept. 4, 1973 APPARATUS FOR CHARGING A LIQUID WITII GAS Franco Tremolada, Via Consale Marcello, 10, Milan, Italy [22] Filed: Feb. 23, 1971 [211 Appl. No.: 118,162

[76] Inventor:

Primary Examiner-Tim R. Miles Assistant ExaminerSteven H. Markowitz Attorney-Karl F. Ross [5 7] ABSTRACT In producing carbonated water, CO gas from a storage tank is introduced into a charging chamber together with a water spray delivered by a double-acting pump. The charged water is collected in a reservoir from which a portion of the evolving gas is directed to the pump for reciprocating same; on its way to the pump, this gas flow passes through a pair of control valves held open by gas pressure from another reservoir outlet as long as the liquid in that reservoir remains below a predetermined level. When this level is reached, a float cuts off the gas pressure so that the control valves close to arrest the pump. Reciprocation of the pump piston is controlled by a switching valve which is temporarily locked in a terminal phase of each piston stroke to stress a spring in a lost-motion coupling between the piston and the valve body, the subsequent release of the locking detent enabling the instant reversal of the switching valve by snap action.

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sum 5 0f 5 ATTORNEY APPARATUS FOR CHARGING A LIQUID WITH GAS My present invention relates to a pumping system to be used in an apparatus for charging a liquid with gas, e.g. in the production of carbonated water.

An object of my invention is to provide means in such a system for supplying water or other liquid under constant pressure to a charging chamber for as long as a reservoir connected with that chamber contains less than a predetermined volume of charged liquid; whenever the reservoir is sufficiently filled, the liquid supply is to be cut off in a manner enabling instant resumption of liquid flow at the prescribed pressure.

Another object of my invention is to provide a double-acting pump of simple design and easy maintenance for delivering the liquid to that chamber under the pressure of e charging gas (such as carbon dioxide) itself, e.g. as evolving within the reservoir from the charged liquid, thus eliminating the need for any external power source.

In accordance with this invention I provide, ina liquid-feeding system of the general character described, a pump in which a pair of inner compartments and a pair of outer compartments are defined by a pair of piston heads on opposite sides of an internal partition of a cylinder or housing, the piston being reciprocated by a motive fluid which. advantageously consists of a portion of the evolving charging gas and which is alternately directed by one or more valves to the two outer compartments. A supply of liquid, such as a-water tap, communicates through respective entrance ports with the two inner compartments from which the liquid is alternately ejected through respective exit ports to the mixing chamber. In the reservoir connected with that chamber, a sensing device such as a float valve cuts off the flow of motive fluid to the pump as soon as a predetermined amount of charged liquid has been stored.

The motive fluid, particularly if constituted by the charging gas, can be simply released into the atmosphere via a low-pressure conduit to which the two outer compartments are alternately connected at the end of each piston stroke by the valve assembly which simultaneously reverses the connection of the gas supply to these compartments; aside from a switching valve required for this operation, the valve assembly may include a pair of shut-off valves in the two conduits controlled by the level sensor in the reservoir to stop and to restart the pump.

Another important feature of my invention resides in the provision of a spring-loaded lost-motion coupling between the pump piston and the switching valve for ing upon one or more retaining balls lodged in lateral holes of the tube and engaging in either of two axially spaced incisions on the stem.

The above and other features of my invention will be described in detail hereinafter with reference to their accompanying drawing in which:

FIG. 1 is a diagrammatic overall view of a system for producing carbonated water in accordance with my invention;

FIG. 2 is an axial sectional view of a pump included in the system of FIG. 1, shown in the upper-dea-center position of its double-acting piston;

FIG. 3 is a view generally similar to FIG. 2 but limited to the region close to the pump axis, showing the piston in an intermediate descending position;

FIG. 4 is a view similar to FIG. 3 with the piston in a terminal phase of its descent;

FIG. 5' is another such view showing the piston at lower dead center;

FIG. 6 is a similar view showing the piston in a terminal phase of its ascending stroke;

FIG. 7 is a framentary cross-sectional view taken on the line VII-VII of FIG. 2;

FIG. 8 is a similar cross-sectional view taken on the line VIII-VIII of FIG. 5;

FIGS. 9 and 10 are cross-sectional views of a first shut-off valve, inserted in a high-pressure conduit for supplying gas to the pump, in closed and in open position, respectively; and

FIGS. 11 and 12 are analogous cross-sectional views of a second shut-off valve located in a low-pressure conduit for venting the spent gas to the atmosphere.

In FIG. 1 I have shown at R a supply of water, which could be a continuously open tap on a water pipe, connected via a check valve 42 in a pipe 41 and a pair of branch pipes 41', 41" with additional check valves 42, 42" to two inner compartments 14, of a pump 1, these compartments being defined inside a cylinder 4 by a transverse partition 8 and two heads l1, 12 (see also FIG. 2) of a double-acting piston. This piston further forms with the pump housing a pair of outer compartments 13, 16, compartment 13 being defined by the top wall 7 of the housing and by the upper piston reversing the latter in a terminal piston position, this coupling including adetent mechanism which locks the piston in a terminal phase of its stroke to stress the loading spring preparatorily to a sudden release to trip the valve by snap action upon a subsequent deactivation of the detent. For ths purpose I prefer to provide the piston with a hollow rod'into which a stem rigid with the movable valve body axially extends for alternate engagement by a pair of spaced-apart abutments within that rod, these abutments being advantageously formed by two sleeves held separated by an interposed compression spring and severing also to shift ferrule on a stationary guide tube surrounding the valve stem, the ferrule being effective in an intermediate position to lock the stem temporarily against axial motion by actlower piston head 12 and the bottom wall 6 of the housing. Inner compartments l4 and 15 also have exit ports leading to branches 43, 43" of a discharge pipe 43 which contain respective check'valves 44' and 44' the several check 'valves referred to prevent any return flow of liquid out of the pump housing by way of the entrance ports of compartments l4 and 15.

The water discharged via pipe 43' arrives under pressure at a spray nozzle 45 of a charging chamber 2 where it is atomized and intimately mixed with a flow of charging gas, specifically C0,, supplied from a tank B via a pipe 46 containing a pressure gauge B. The mixture of water and gas passes from chamber 2 through drain 47 into a reservoir 3 which it is desired to keep filled up to a maximum level L. A syphon tube 48 rises from the bottom of the reservoir to facilitate the drawing of liquid therefrom to a destination U; two conduits 49 and 50 extend from the top of the reservoir to carry off evolving gases. The inlet end of conduit 50 confronts a stopper 57 within a nipple 56, this stopper being carried on a stem of a floating ball 54 so as to obstruct that inlet whenever the liquid in the reservoir rises to the level L.

The reciprocation of the pump piston is controlled by a switching valve 18 in the base of the pump housing 4, this valve lying at the junction of a high-pressure conduit 19 connected with line 49 via a shut-off valve 51, a low-pressure conduit 21 leading to the atmosphere by way of another shut-off valve 52 and an extension 21', a chennel 21 extending to the distal (i.e. upper) outer compartment 13, and a passage 33 communicating with the proximal (i.e. lower) outer compartment 16. with shut-off valves 51 and 52 open, switching valve 18 operates in a manner more fully described hereinafter to direct gas from conduit 19 alternately into channel 20 and passage 33 to pressurize one of the two outer compartments while venting the other of these compartments through conduit 21 and its extension 21 to the atmosphere. Valves 51 and 52 are controlled by gas pressure from line 50 via branches 50 and thereof, being held open whenever the inlet of that line is unblocked whereby the pump '1 keeps operating until the liquid in reservoir 3 reaches the level L; when this occurs, stopper 57 obstructs the tube 50 which has a restricted termination 53 opening into the atmosphere by way of conduit extension 21'.

The structural details of switching valve 18 and its control mechanism will now be described with reference to FIGS. 2-8. As shown particularly in FIGS. 2-6, the piston has a hollow stem interconnecting its heads 11 and 12 which bear in a fluid-tight manner upon the inner wall surface of cylinder 4 by way of packing rings 11a, 12a. Similar packing rings 5' and 5" between the cylinder wall and the end walls 6 and 7 of the pump housing seal the interior thereof against the atmosphere while a further packing ring 9 engages the piston rod 10 in partition 8.

The bottom wall or base 6 of the pump housing forms a socket 17 which accommodates the body 27 of switching valve 18 and, like that body, is of generally prismatic shape with a pair of parallel wall surfaces 17, 17" separated by a distance 11 (FIGS. 7 and 8) slightly exceeding the thickness of the frame-shaped valve body. Two independently transversely displaceable members 37 and 38, embraced by a mounting ring 36 snugly fitting within the opening 34 of valve body 27, are normally separated by a small gap, this separation being maintained by an elastically deformable annular gasket 39 received in a peripheral recess of the generally disk-shaped member 37. The other member 38, confronting the socket surface 17, is ring-shaped and forms an annular shoulder projecting toward that surface beyond the frame 27 and the mounting ring 36. Disk member 37 has a concave front face next to ring member 38, this front face forming a recess 40 as a continuation of the opening of the ring member; the opposite, rear face of member 37 has a shallow depression 37' confronting the wall surface 17". The terminations of gas conduits l9 and 21 and of connecting channel 20 open at axially spaced locations into the socket 17 at its surface 17, the termination of channel 20 being bracketed by those of conduits 19 and 21 in such a way that this channel communicates only with conduit 19 in a raised position of valve body 27 (FIG. 7) and only with conduit 21 in a lowered position of that valve body (FIG. 8). In the first instance, gas pressure from conduit 19 enters the recess 40 and urges the disk 37 into firm contact with surface 17" while also deforming the gasket 39 to press the ring 38 against surface 17; in the second instance the high-pressure gas enters the socket 17 directly, outside the valve members 37 and 38, and forces its way to the depression 37 of disk 37 to urge it together with ring 38 into sealing engagement with surface 17. In each case, therefore, gas leakage between the high-pressure and lowpressure sides of the system will be minimized.

A stem 26 rigid with valv body 27 extends axially upwardly into the hollow piston rod 10 and terminates at its upper end in a beveled shoulder 26'. The lower part of the stem is surrounded by a guide tube 23 which has a base 22 held onto housing wall 6 by a retaining plate 22'. Tube 23 is provided near its upper end with two or more holes 24 accommodating balls 25 whose diameter slightly exceeds the wall thickness of the tube and which are partly receivable in annular grooves 29 and 29' formed at axially spaced locations in the stem 26. A furrule 30 slidably embraces the tube 23 and is frictionally retained thereon by at least one of two axially spaced packing rings 23', 23" engageable with a portion 30' thereof having a reduced inner diameter. The lower end of tube 23 fits between a pair of humps 27' of valve body 27 in a manner enabling circulation of gas between socket 17 and compartment 16 via a clearance 33 in any position of valve body 27 and piston head 12. A sleeve 35, freely slidable within piston rod 10, has a bottom flange 32 with an inwardly projecting annular shoulder 32' by which it comes to rest on the humps 27 in the terminal phase of the descending piston stroke (FIG. 4). Another sleeve 28, also freely slidable in piston rod 10, surrounds the upper end of stem 26 and is urged away from sleeve 35 by an enveloping coil spring 31; sleeve 28 is in line with tube 23 and has its lower end formed with a beveled internal shoulder 28' engageable with the beveled shoulder 26' of stem 26 in the terminal phase of the ascending piston stroke (FIG. 6). The outer diameter of sleeve 28 is the same as that of ferrule 30 which is engaged by the sleeve 28 toward the end of the descending stroke as shown in FIG. 4.

As seen in FIGS. 9 and 10, valve 51 has a housing into which the conduits 19, 49 and 50 open, an insert 61 within this housing forming a seat for a valve cone 62 which is urged by a spring 59 into a postion (FIG. 9) blocking communication between conduits l9 and 49. A piston head 58 secured to valve cone 62 drives the latter upwardly, against the force of spring 59, in respone to gas pressure in conduit 50 so that gas from conduit 49 enters the conduit 19 (FIG. 10). In an analogous manner, as shown in FIGS. 11 and 12, the housing 60' of valve 52 has an insert 61' which forms a seat for a valve cone 62' urged by a spring 59 into a closing position to disconnect conduit 21 from its extension 21'; in the presence of gas under pressure in conduit 50", a piston head 58 rigid with valve cone 52 is driven upwardly to vent the conduit 21 to the atmosphere via its extension 21.

With valves 51 and 52 open, the operation of the pump shown in FIGS. 2-8 is as follows.

In the upper-dead-center position illustrated in FIG. 2, the valve body 27 has been raised by the upward entrainment of its stem 26 by the sleeve 28 through the interengagement of their respective flanges 26 and 28. In this position of valve 18, also shown in FIG. 7, gas under pressure of conduit 19 is directed by valve members 37 and 38 into channel 20 and reaches the upper outer compartment 13 to drive the piston 0-12 down. At this stage the ferrule 30 is elevated above its locking position, through its engagement with the internal shoulder 32' of sleeve 35, so that the balls 25 are not restrained against limited outward movement to an extent permitting an axial shifting of stem 26. Since, however, the valve body 27 is frictionally retained in its socket 17 by the gaspressure, as previously explained, there is no tendency for the stem to shift downwardly even after the piston has begun its descent so that the flange 28' of sleeve 28 disengages the flange 26' of the stem as shown in FIG. 3.

Next, as illustrated in FIG. 4, the piston reaches a position in which the lower end of sleeve 28 comes to rest on ferrule 30 to drive its reduced-diameter portion 30' down past an intermediate locking position in which it engages the retaining balls 30'. Substantially simultaneously with the temporary immobilization of its valve body 27, its humps 27' intercept the sleeve 35 to prevent any further descent thereof so that spring 31 is compressed between the two sleeves. Shortly thereafter, just before the upper piston head 11 reaches the top of stem 26, ferrule 30 is depressed sufficiently to release the balls 25 whereupon the spring 31 instantly expands and drives the valve body 27 into its alternate position (FIG. 8) by a snap action.

With the piston now in its lower-dead-center position, as illustrated in FIG. 5, its stroke is reversed as high-pressure gas from conduit 19 enters the socket l7 and finds its way into the lower outer compartment 16 through the clearance 33'between the hump 26 and the tube base 22, this clearance corresponding to the passage 33 indicated diagrammatically in FIG. 1. With the piston rising into the position of FIG. 6, the shoulder 32 of sleeve 35 entrains the ferrule 30 upwardly so that, again the valve stem 26 is temporarily immobilized as the spring 31 is being compressed between the two sleeves 28 and 35. Sleeve 28, being retained at this point by its flange 28 coacting with flange 26"of stem 26, cannot follow the rise of the piston until the latter reaches its top-dead-center position shown in FIG. 2 whereupon the release of the detent balls 25 by the lifting of ferrule 30 allows the spring 31 to re-expand and, again by snap action, to restore the valve 18 to its previous position. The cycle can then be repeated.

It will thus be seen that I have provided a pump which instantly reverses the stroke of its double-acting piston so that the flow of water to the charging chamber 2 is I virtually continuous and under constant pressure. Naturally, this pump could also be used in a system in which the liquid propelled by the pump is used for a different purpose, yet the availability of gas pressure to drive the pump is particularly advantageous in an apparatus for making carbonated water.

Some of the features describedabove, including the reversal of the pumpint stroke under the control of a floating member,could also be realized with valves that are operated electrically instead of pneumatically, e.g. with the aid of a microsensitive switch operated by the float 54. The driving gas entering the conduit 49 could also be taken directly from the tank B rather than from the reservoir 3.

I claim:

I. In a system for charging a liquid with gas, in combination:

a supply of liquid to be charged;

storage means containing a charging gas under pressure; 1

. a charging chamber provided with a first inlet for said liquid and a second inlet connected to said storage means;

a pump for delivering said liquid to said chamber,

said pump comprising a cylinder with a doubleacting piston having a pair of spaced-apart heads, said cylinder being provided with an internal partition between said heads defining with the latter a pair of inner compartments each having an entrance port connected to said supply and an exit port connected to said first inlet, said cylinder having end walls defining with said heads a pair of outer compartments;

a source of motive fluid for said pump;

valve means operable to connect said source alternately to said outer compartments for reciprocating said piston;

a reservoir for gas-charged liquid connected to said chamber;

sensing means responsive to the amount of liquid in said reservoir;

and control means for said valve means operable by said sensing means to cut off the flow of motive fluid to said pump upon said amount of liquid reaching a predetermined magnitude.

2. The combination defined in claim 1 wherein said pump is provided with a first pair of check valves ahead of said entrance ports and a second pair of check valves beyond said exit ports.

3. The combination defined in claim 1 wherein said pump is provided with a high-pressure conduit originating at said source and with a low-pressure conduit opening into the atmosphere, said valve means including a switching valve for alternately connecting said outer compartments to said high-pressure conduit and said low-pressure conduit, respectively, said valve means further including a pair of shut-off valves in said conduits controed by said sensing means.

4. The combination defined in claim 3 wherein said reservoir is provided with a discharge line for evolving gases with a restricted termination opening into the atmosphere and with branches leading to said shut-off valves, said sensing means comprising a floating member in said reservoir positioned to obstruct said discharge lines upon a rise of the liquid to a predetermined level.

5..The combination defined in claim 4 wherein said source is an outlet of said reservoir connected to said high-pressure conduit.

6. The combination defined in claim 3 wherein said piston has a hollow rod interconnecting said heads, said switching valve comprising a valve body provided with an axially extending stem lodged in said rod, a springloaded lost-motion coupling in said rod linking same with said stem for temporarily immobilizing same in a terminal phase of each reciprocating stroke of the piston, deactivation of said detent means in a dead-center position of said piston resulting in an instant reversal of said switching valve.

7. The combination defined in claim 6 wherein one of said end walls is formed with a socket communicating with said conduits and opening into a passage leading to the proximal one of said outer compartments, said pump being further provided with a channel connecting said socket with the distal one of said outer compartments, said valve body being shiftable in said socket for alternately connecting said conduits with said passage and said channel, respectively.

8. The combination defined in claim 7 wherein said socket has a wall surface provided with terminations of said conduits and said channel at axially spaced locations, the termination of said channel being bracketed by the terminations of said conduits, said valve body having an annular shoulder bearing upon said wall surface in a fluidtight manner and surrounding a recess confronting one pair of adjoining terminations in a first postion and another pair of adjoining terminations in a second position.

9. The combination defined in claim 8 wherein said valve body comprises a frame parallel to and spaced from said wall surface, a disk member and a ring member seated side by side in said frame with relative transverse mobility and with formation of a peripheral gap therebetween, said ring member projecting toward said wall surface to form said annular shoulder, and an elastically deformable annular gasket in said gap tending to spread said members apart against said wall surface and an opposite surface of said socket.

10. The combination defined in claim 9 wherein said disk member has a concave front face next to said ring member forming part of said recess, said disk member further having a rear face with a depression accessible to high-pressure gas in said socket for urging both said members toward said wall surface.

1 l. The combination defined in claim 6 wherein said lost-motion coupling comprises a guide tube for said stem rigid with one of said end walls, said tube being formed with a lateral hole and being provided with a ball of a diameter greater than the wall thickness of said tube seated in said hole, said stem having a pair of axially spaced incisions alternately engageable by said ball for locking said valve body in either of two operating positions thereof, a ferrule inside said rod surrounding said tube in the region of said hole with frictional fit but axial displaceability between two extreme positions out of line with said ball, and a pair of axially spaced abutments in said rod engaging said ferrule in opposite terminal piston positions for moving through an intermediate locking position aligned with said ball to immobilize said stem temporarily just before the end of each stroke.

12. The combination defined in claim 11 wherein said abutments form part of two relatively movable elements in said rod, said coupling including an expanding spring tending to spread said elements axially apart, said elements being respectively engageable with said stern in opposite terminal positions of said piston for shifting said valve body upon movement of said ferrule past said locking position.

13. The combination defined in claim 12 wherein said elements are a first sleeve, coaxially surrounding said stem and said ferrule, and a second sleeve in line with said guide tube, said valve body having a pair of projections alongside said stem engageable by said first sleeve, said stem having a flanged end engageable by an internal flange of said second sleeve.

0 l l I I! 

1. In a system for charging a liquid with gas, in combination: a supply of liquid to be charged; storage means containing a charging gas under pressure; a charging chamber provided with a first inlet for said liquid and a second inlet connected to said storage means; a pump for delivering said liquid to said chamber, said pump comprising a cylinder with a double-acting piston having a pair of spaced-apart heads, said cylinder being provided with an internal partition between said heads defining with the latter a pair of inner compartments each having an entrance port connected to said supply and an exit port connected to said first inlet, said cylinder having end walls defining with said heads a pair of outer compartments; a source of motive fluid for said pump; valve means operable to connect said source alternately to said outer compartments for reciprocating said piston; a reservoir for gas-charged liquid connected to said chamber; sensing means responsive to the amount of liquid in said reservoir; and control means for said valve means operable by said sensing means to cut off the flow of motive fluid to said pump upon said amount of liquid reaching a predetermined magnitude.
 2. The combination defined in claim 1 wherein said pump is provided with a first pair of check valves ahead of said entrance ports and a second pair of check valves beyond said exit ports.
 3. The combination defined in claim 1 wherein said pump is provided with a high-pressure conduit originating at said source and with a low-pressure conduit opening into the atmosphere, said valve means including a switching valve for alternately connecting said outer compartments to said high-pressure conduit and said low-pressure conduit, respectively, said valve means further including a pair of shut-off valves in said conduits controed by said sensing means.
 4. The combination defined in claim 3 wherein said reservoir is provided with a discharge line for evolving gases with a restricted termination opening into the atmosphere and with branches leading to said shut-off valves, said sensing means comprising a floating member in said reservoir positioned to obstruct said discharge lines upon a rise of the liquid to a predetermined level.
 5. The combination defined in claim 4 wherein said source is an outlet of said reservoir connected to said high-pressure conduit.
 6. The combination defined in claim 3 wherein said piston has a hollow rod interconnecting said heads, said switching valve comprising a valve body provided with an axially extending stem lodged in said rod, a spring-loaded lost-motion coupling in said rod linking same with said stem for temporarily immobilizing same in a terminal phase of each reciprocating stroke of the piston, deactivation of said detent means in a dead-center position of said piston resulting in an instant reversal of said switching valve.
 7. The combination defined in claim 6 wherein one of said end walls is formed with a socket communicating with said conduits and opening into a passage leading to the proximal one of said outer compartments, said pump being further provided with a channel connecting said socket with the distal one of said outer compartments, said valve body being shiftable in said socket for alternately connecting said conduits with said passage and said channel, respectively.
 8. The combination defined in claim 7 wherein said socket has a wall surface provided with terminations of said conduits and said channel at axially spaced locations, the termination of said channel being bracketed by the terminations of said conduits, said valve body having an annular shoulder bearing upon said wall surface in a fluidtight manner and surrounding a recess confronting one pair of adjoining terminations in a first postion and another pair of adjoining terminations in a second position.
 9. The combination defined in claim 8 wherein said valve body comprises a frame parallel to and spaced from said wall surface, a disk member and a ring member seated side by side in said frame with relative transverse mobility and with formation of a peripheral gap therebetween, said ring member projecting toward said wall surface to form said annular shoulder, and an elastically deformable annular gasket in said gap tending to spread said members apart against said wall surface and an opposite surface of said socket.
 10. The combination defined in claim 9 wherein said disk member has a concave front face next to said ring member forming part of said recess, said disk member further having a rear face with a depression accessible to high-pressure gas in said socket for urging both said members toward said wall surface.
 11. The combination defined in claim 6 wherein said lost-motion coupling comprises a guide tube for said stem rigid with one of said end walls, said tube being formed with a lateral hole and being provided with a ball of a diameter greater than the wall thickness of said tube seated in said hole, said stem having a pair of axially spaced incisions alternately engageable by said ball for locking said valve body in either of two operating positions thereof, a ferrule inside said rod surrounding said tube in the region of said hole with frictional fIt but axial displaceability between two extreme positions out of line with said ball, and a pair of axially spaced abutments in said rod engaging said ferrule in opposite terminal piston positions for moving through an intermediate locking position aligned with said ball to immobilize said stem temporarily just before the end of each stroke.
 12. The combination defined in claim 11 wherein said abutments form part of two relatively movable elements in said rod, said coupling including an expanding spring tending to spread said elements axially apart, said elements being respectively engageable with said stem in opposite terminal positions of said piston for shifting said valve body upon movement of said ferrule past said locking position.
 13. The combination defined in claim 12 wherein said elements are a first sleeve, coaxially surrounding said stem and said ferrule, and a second sleeve in line with said guide tube, said valve body having a pair of projections alongside said stem engageable by said first sleeve, said stem having a flanged end engageable by an internal flange of said second sleeve. 